1. Field of the Invention
The present invention relates to an ignition device attachment structure, and more particular, to an ignition device attachment structure for an internal combustion engine.
2. Background of the Invention
There has been known an internal combustion engine in which an ignition plug tube is inserted between an ignition device insertion hole formed in a cylinder head and a cylinder head cover (see e.g. Japanese Patent Laid-Open No. 2007-327378). In this internal combustion engine, an ignition plug as the ignition device is inserted into the ignition plug tube and then inserted into the ignition device insertion hole.
In the above-mentioned traditional configuration, however, a projecting object may be installed on an upper portion of the cylinder head, or accessories may be arranged above the cylinder head. In such a case, they become obstructive so that the ignition plug cannot be inserted vertically to the cylinder head. Therefore, the ignition plug has to be arranged at a slant to avoid the projecting object or accessories. If the ignition plug is inclined too much, the ignition plug interferes with a rocker arm or a valve. It is necessary, therefore, to increase an angle formed between an intake valve and an exhaust valve, which poses a problem with the increased width of the cylinder head.